any substance that can be used for economic gain
what is available
what is an acceptable form at an acceptable price
Petroleum, Natural Gas, and Coal
Type of coal that has high moisture and high volatiles
Type of coal with medium moisture and medium volatiles
Type of coal that has low moisture and low volatiles. Also has high carbon.
Type of mining that scars land and pollutes nearby water supplies
Type of gas mostly made up of carbon, hydrogen and oxygen
Type of gas mostly made up of methane.